Molecular Cloning of a $\beta$-D-Galactosidase Gene from Lactococcus lactis subsp. lactis 7962

  • CHANG, HAE-CHOON (Department of Food and Nutrition, Chosun University) ;
  • YANG-DO CHOI (Department of Agricultural Chemistry, Research Center for New Bio-materials in Agriculture, Seoul National University) ;
  • HYONG-JOO LEE (Department of Food Science and Technology, Research Center for New Bio-materials in Agriculture, Seoul National University)
  • Published : 1996.12.01

Abstract

The ${\beta}$-galactosidase gene from Lactococcus lactis subsp. lactis ATCC 7962 was cloned and its enzymatic properties were characterized, with a view to assessing its potential use as a selection marker in the food-grade cloning vector. Chromosomal DNA from L. lactis subsp. lactis 7962 was cleaved with PstI and ligated into pBR322 for transformation into Escherichia coli TGl. Transformants showing ${\beta}$-galactosidase activity possessed the pBR322 plasmid containing a 10 kilobase (kb) PstI fragment and this plasmid was named pCKL11. The cloned ${\beta}$-galactosidase gene came from the chromosomal DNA of L. lactis subsp. lactis 7962 was confirmed by Southern hybridization. A restriction map of pCKL11 was constructed from the cleavage of both pCKL11 and the purified 10kb insert fraqment. The. optimum pH of the ${\beta}$-galactosidase determined with the E. coli harboring the pCKL11 was 7.0. The optimum temperature was $50^{\circ}C$, while the pI of the enzyme was 7.4. These values were the same as those of the enzyme from the parent strain.

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